I have a 455 block machined to .03 oversized. Sorry if my terminology is wrong here, I'm a newbie when it comes to this kind of stuff. Is there any big advantage or disadvantage to having it bored to .03, .04, or .06? Also does this have an effect on the heads that I will one day need to rebuild this engine. o No:
I'm not an expert on the subject my self, but I'll try to help you out as best I can. The advantage to boring out a cylinder is to remove scratches, grooves, etc. that are worn into the cylinder walls by the rings. It does increase the displacement of the engine but not by much. The drawback, especially with Buicks is if you go too large, the cylinder walls will be too thin. I don't think you need to do anything special to the cylinder heads though.
.040 may be too much and .060 is too much. No real power to be gained there relative to porting heads, changing to TA Al heads, recurving the dist., installing the right carb. or headers etc.
Their could be a substantial power gain depending on pistons being used. .060 over on a 455 will bring you out to 468 cubes. When you increase bore size you also increase your compression raito, more piston area.
I recently had a conversation with a bud who races C/SA. He asked me this hypothetical question. If you put a bore guage in one of the two mid cylinders, installed front to rear, extend it .001 or .002 extra to make it stay, then squeeze the outside and the inside of the block together, would the guage stay or fall out? So we tried it on a Chevy 396 block. It does fall out. Interesting how soft the blocks really are.
Rus,a couple of advantages of boring vs. stroking worth considering. Larger bores will unshroud the valves considerably allowing better breathing capacity. Also boring for cubic inches will offer less frictional losses than by stroking. You should really consider having your block sonic checked for cylinder wall thickness (full circle and full length of bore). Here are some parameters to use--with unfilled water jackets, cylinder bore thickness should be .150" minimum, with water jackets filled to within 1.5" of the deck can run with as little as .110" and with water jackets completely filled you can run with as little as .075" wall thickness(minimum dimension at thinnest point). Hope this helps.
